Dual band blade antenna with filtering and matching network on blade



Oct. 5, 1965 M. v. ANDERSON ETAL 3,210,764

DUAL BAND BLADE ANTENNA WITH FILTERING AND MATCHING NETWORK ON BLADE 2 Sheets-Sheet 1 Filed Dec. 29, 1961 INVENTORS MARD/S V. ANDERSON BYLAWRE/VCE P. VALE/V676 QM Y ATTORNEYS Oct. 5, 1965 M. v. ANDERSON ETAL 3,210,764

DUAL BAND BLADE ANTENNA WITH FILTERING AND MATCHING NETWORK ON BLADE Filed Dec. 29. 1961 2 Sheets-Sheet 2 MA/PO/S 1/. ANDERSON BY LAWRENCE I? VALE/V676 United States Patent Ofi ice 3,210,764 DUAL BAND BLADE ANTENNA WITH FILTERING AND MATCHING NETWORK N BLADE Mardis V. Anderson, Richardson, Tex., and Lawrence P. Valencic, Marion, Iowa, asignors to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Filed Dec. 29, 1961, Ser. No. 163,194 7 Claims. (Cl. 343-708) This invention pertains to an antenna structure and more particularly to a lightweight aircraft antenna capable of utilization on dual radio frequency bands.

vIt is oftentimes desirable to utilize a minimum number of antennas for a multiplicity of purposes. This is especially true in the case of aircraft antennas where it is extremely desirable to keep an antenna as small and lightweight vas possible and, in addition, keep the number of antennas required to a minimum.

It has been common, especially in the case of aircraft antennas, to provide a thin blade-like monopole projecting outwardly from the fuselage to transmit and receive radio signals in the VHF range of frequencies. While a similar antenna might also be provided for radio frequencies in the UHF range of frequencies, it has not been possible heretofore to provide an antenna having both the necessary compactness and frequency range (with sufficient power transfer) to enable utilization of the antenna for transmitting and receiving radio signals in both the VHF and UHF frequency ranges.

It is therefore an object of this invention to provide a lightweight and compact blade-like antenna that is capable of transmitting and receiving radio signals both in the UHF and VHF frequency ranges.

More particularly, it is an object of this invention to provide a broad monopole one side of which serves as the radiating element while the other side has filtering and matching components mounted thereon in a manner such that said monopole may be utilized in dual frequency bands without appreciably increasing the size or weight of the antenna.

It is another object of this invention to provide an antenna structure an import-ant element of which is a printed circuit board having an insulating central portion, a conductive portion on one side of said central portion which serves as a radiating element and a conductive portion on the other side of said central portion formed in a predetermined manner to provide matching and filtering so that the resulting antenna structure is usable for transmitting and receiving in dual frequency bands one of which is in the VHF range of frequencies while the other is in the UHF range of frequencies With these and other objects in view, which will become apparent to one skilled in the art as the description proceed-s, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein described invention may be included as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and wherein:

FIGURE 1 is a perspective view of the antenna of this invention illustrating matching and filtering elements thereon;

FIGURE 2 is a perspective view of the opposite side of the broad monopole shown in FIGURE 1 illustrating the radiating element;

FIGURE 3 is a sectional view taken through 3-3 of FIGURE 1; and

3,210,764 Patented Oct. 5, 1965 FIGURE 4 is an enlarged view of the VHF connector shown in FIGURE 1.

Referring now to the drawings, the numeral 7 refers generally to the broad monopole, which monopole is preferably .a printed circuit board having a central layer 9 of insulating material with a relatively thin layer of conductive material, usually copper, on each side.

As shown best in FIGURE 2, conductive layer 11, which serves as the radiating element, substantially covers one side of insulating layer 9 with the bottom edge 12 sloping downwardly from each side toward the middle so that the bottom edge is substantially V shaped. As shown best in FIGURE 1, matching and filtering elements '13 have been formed on the side of insulating layer 9 opposite that of radiating element 11, which elements may be conventionally formed, such as, for example, by a silk screen and etching process. By placing matching and filtering elements .13 on the broad monopole, radiating element 1 1 also serves as a ground plane for the printed circuit matching and filtering elements.

In order to more clearly illustrate the antenna of this invention, no attempt has been made to scale the drawings. For example, radiating element 11 is preferably 13 to 14 inches in height and about 6 inches in Width, while the thickness is extremely small with respect thereto since the insulating layer need only be about one-eighth of an inch in thickness and the copper deposited on each side only about 0.005 inch in thickness. In the completed antenna, however, the over-all thickness is more substantial due to the protective coverings placed thereon. The broad monopole is preferably adapted for connectionto the fuselage of an aircraft or the like to act as a vertically polarized antenna. As shown in the drawings, this may be accomplished, for example, by fastening the broad monopole, by means of screws 17', to blocks 18' located near the two bottom corners of the monopole." Bottom edge 19 of the monopole may then be brought into, and held in, normally disposed engagement with 'a streamlined mounting plate 23 conventionally, as with screws (not shown) for example. Plate 23 has holes 24 therein for adapting the plate for attachment to the fuselage of an aircraft or the like, both mechanically and electrically, so that the mounting plate and fuselage can act 1 as the ground plane for the antenna.

The VHF signal is coupled to theantenna when trans mittin-g (and away from the antenna when receiving) through connector 28, which connector is secured to' mounting plate 23 conventionally, as by means of .a fas- .tening nut 29 (nut 29 and mounting plate 23 are thus electrically connected), and has a terminal 30, insulated from the mounting plate and nut, projecting upwardly toward the broad monopole (which is notched along the bottom edge, as at '31, to provide for the connector).

In like manner, the UHF signal is coupled to and from the antenna through connector 33, which connector is .secured to plate 23 conventionally, as by fastening nut 34 (which nut is also electrically connected to mounting plate 23), and has a terminal 35, insulated from the mounting plate and nut, projecting upwardly toward the broad monopole (which is notched along the bottom edge, as at 36 to receive connector 33),

Coaxial cable 40 connects VHF connector 28 to the broad monopole and at one end has its inner conductor connected to terminal 30 and its outer conductor connected to fastening nut 29, as shown best in FIGURE 4. In like manner, coaxial cable 42 connects the UHF connector 33 to the broad monopole and at one end [has its inner conductor connected to terminal 35 and its outer conductor connected to fastening nut 34 in the same manner as shown in FIGURE 4.

Coaxial cables and 42 are preferably maintained as short as possible and are preferably in engagement (after a short distance from the connectors) with the broad monopole at the matching and filtering element side thereof. As shown in FIGURE 1, the cables are brought into contact with the monopole at the bottom edge 19 and the outer conductors are maintained in electrical contact with conductive element 44 of matching and filtering elements 13, preferably by soldering.

At point 45 (where, as shown in FIGURE 1, the outer conductors of the coaxial cables are soldered to conductive element 44), the outer conductors of the cables terminate electrical engagement with inductive element 44 and are then laid along and on top of a thin strip of conductive material 46 to point 47 where the outer conductors of the coaxial cables 40 and 42 and the thin conductive strip 46 are connected through the insulating layer 9 to radiating element 11. This connection is also made by soldering, as is conventional. Thus, thin strip 46 and radiating element 11 form a high impedance transmission line.

The thin conductive strip 46 extending from point 45 to point 47 is of a predetermined length, which length is chosen to be equal to one quarter wavelength for the middle frequency of the highest frequency band covered. Thus, with the antenna usable in one band of frequencies in the VHF range (for example, 116 to 152 megacycles) and one band of frequencies in the UHF range (for example, 225 to 400 megacycles), the one quarter wavelength stub is chosen for the middle frequency of the UHF band covered (for example, 312.5 megacycles).

From point 47, the coaxial cables 40 and 42 engage insulating portion 9, not necessarily remaining adjacent to one another (as shown in FIGURE 1), to points 49 and 50 where the inner conductors of UHF and VHF coaxial cable 42 and 40 terminate in connections to the UHF and VHF filtering and matchining elements 52 and 53, respectively, while the outer conductors are connected through central layer 9 to radiating element 11, as by soldering. It has been found preferable that coaxial cables 40 and 42, when laid together on the board, he positioned with coaxial cable 42 between coaxial cable 40 and the broad monopole.

As shown in FIGURE 1, UHF filtering and matching element 52 may include a tapered line 55 which line is connected at its higher impedance end to the inner conductor of coaxial cable 42 and at its lower impedance end to serially connected printed circuit inductive element 56 and printed circuit capacitive element 57. In addition, the lower impedance end of tapered line 55 is also y connected through capacitor 58 to printed circuit inductive element 59, the other end portion of which is connected through insulating layer 9 to radiating element 11, as by soldering, at 60. Capacitor 61 and printed circuit lead 62 (inductive element) connect capacitor 58 and inductive element 59 to conductive element 44.

As also shown in FIGURE 1, VHF filtering and matching element 53 may include printed circuit capacitor elements 65 and 66, the latter of which is connected by means of printed circuit inductive element 67 to a second printed circuit inductive element 68, element 68 serving as a lead connected to element 67 at one end, to capacitor element 65 near the middle, and to printed circuit lead 62 at the other end.

Printed circuit inductive elements 56 and 6t printed circuit capacitive element 57 and capacitors 58 and 61 form a high pass filter, which filter is complementary to the low pass filter formed by printed circuit capacitive elements 65 and 66 and printed circuit inductive elements 67 and 68. In addition, printed circuit elements 44 and 62 are, of course, of such length and width as to assist in matching the antenna impedance to the characteristic impedances of the filters.

It is to be appreciated that the filtering and matching elements shown herein are merely illustrative and may be varied, as would be obvious to one skilled in the art, depending upon the dual frequency ranges to be covered.

In operation, the antenna of this invention is substantially resonated for transmitted and received radio signals in both the VHF and UHF ranges (116-152 megacycles and 225400 megacycles), and there is little interaction between the bands. The nominal impedance on both bands of frequencies covered is 50 ohms. When a signal in the covered UHF range is transmitted or received, the quarter wavelength stub 46 is essentially not a factor since the stub is resonant at the middle frequency of the UHF frequency band covered, and filtering and matching elements 52 therefore match the antenna to the input line to maximize power transfer.

When a signal in the covered VHF range is transmitted or received, the quarter Wavelength stub 46 now acts essentially as an inductive element for these frequencies. Thus stub 46 acts in conjunction with filtering and matching elements 53 to match the antenna to the input line to maximize power transfer for signals in the VHF frequency band covered.

In view of the foregoing, it should be obvious to one skilled in the art that the structure of this invention provides a novel lightweight and compact antenna that is usable for dual frequency bands.

What is claimed as our invention is:

1. A dual frequency antenna, comprising: a broad monopole having a conductive radiating layer and an insulating layer; a first terminal for receiving a radio signal at a frequency within a predetermined range of frequencies; a first coaxial cable having one end connected to said first terminal; a second terminal for receiving a radio signal at a frequency within a predetermined second range of frequencies, said second range of frequencies being lower than said first range of frequencies; a second coaxial cable having one end connected to said second terminal; first and second filtering and matching networks on said insulating layer; first connecting means connecting the outer conductor of said coaxial cable to said filtering and matching networks; second connecting means connecting the outer conductor of said coaxial cables to said radiating layer; a thin conductive strip connected to said first and second connecting means, said thin strip being of a length equal to one-quarter of a wavelength of a particular frequency within said first range of frequencies; and third connecting means connecting the inner conductor of said coaxial cables to said filtering and matching networks so that said first filter and matching network substantially resonates said antenna for frequencies in said first range of frequencies and said second filtering and matching network acting in conjunction with said quarter wavelength strip substantially resonates said antenna for frequencies within said second range of frequencies.

2. The antenna of claim 1 wherein said first range of frequencies is in the UHF range and said second range of frequencies is in the VHF range.

3. The antenna of claim 1 wherein said filter and matching networks include printed circuit elements in engage ment with said insulating layer of said broad monopole at the side opposite said radiating layer.

4. The antenna of claim 1 further characterized by agrounded mounting plate upon which said broad mono-- pole is mounted and wherein said radiating element ter-- minates substantially at a point near said grounded mounting plate.

5. A dual frequency aircraft antenna comprising: a printed circuit board having a center layer of insulating material, a first outer layer of conductive material substantially covering one side of said center layer to form a radiating element, said radiating element terminating near the bottom edge of said insulating layer, and a second outer layer covering a portion of the other side of the said center layer, said second outer layer being formed to provide first and second printed circuit filter and match ing networks; a grounded conductive mounting plate fastened to the bottom edge of said insulating layer; a first terminal for receiving a radio signal within a band of frequencies in the UHF range; a second terminal for receiving a radio signal within a band of frequencies in the VHF range; a first antenna coupling coaxial cable one end of which has the inner conductor connected to said first terminal and the outer conductor connected to said mounting plate; a second antenna coupling coaxial cable one end of which has the inner conductor connected to said second terminal and the outer conductor connected to said mounting plate; said coaxial cables extending onto said printed circuit board at said matching and filtering element side thereof; first connecting means connecting the outer conductor of said coaxial cables to said matching and filtering elements at one side thereof; second connecting means connecting the outer conductor of said coaxial cables to said radiating layer through said insulating layer; a thin conductive strip connected between said first connecting means and said second con necting means, said thin strip being of a length substantially equal to one quarter wavelength of the middle frequency of said UHF band of frequencies covered; and means connecting the inner conductors of said first and second coaxial cables to said first and second filtering and matching networks at the other side of each said network, respectively, whereby said first filtering and matching network substantially resonates said antenna for the frequencies in said covered UHF band and said second filtering and matching network in conjunction with the inductive reactance of said quarter Wavelength strip at said VHF frequencies substantial resonates said antenna for the frequencies in said covered VHF band.

6. A dual frequency antenna, comprising: a broad monopole having a radiating layer and an insulating layer; a first terminal for receiving a radio signal at a frequency within a predetermined range of frequencies;

first cable means connected to said first terminal; a second terminal for receiving a radio signal at a frequency within a second predetermined range of frequencies, said second range of frequencies being appreciably lower than said first range of frequencies; second cable means connected to said second terminal; a matching and filtering network on said broad monopole at said insulating layer side thereof; and means connecting said cable means to said radiating layer and to said matching and filtering network so that said antenna is substantially resonated for both said first and said second ranges of frequencies and is capable of receiving and transmitting radio signals in both said ranges of freqeuncies without appreciable interaction therebetween.

7. A dual frequency antenna, comprising: a broad monopole having a thin insulating layer between a thin radiating layer and a filtering and matching network formed at least in part by thin conductive material; first and second terminals for receiving radio signals within first and second frequency bands; and means connecting said terminals to said radiating element and to said filtering and matching network whereby said antenna is substantially resonated for radio signals is both said first and second frequency bands.

References Cited by the Examiner UNITED STATES PATENTS 2,505,751 5/50 Bolljahn 343-705 X 2,949,606 8/60 Dorne 343-708 2,994,876 8/61 Josephson 343831 X 3,039,095 6/62 Josephson 343708 FOREIGN PATENTS 654,707 6/51 Great Britain.

HERMAN KARL SAALBACH, Primary Examiner. 

1. A DUAL FREQUENCY ANTENNA, COMPRISING: A BROAD MONOPOLE HAVING A CONDUCTIVE RADIATING LAYER AND AN INSULATING LAYER; A FIRST TERMINAL FOR RECEIVING A RADIO SIGNAL AT A FREQUENCY WITHIN A PREDETERMINED RANGE OF FREQUENCIES; A FIRST COAXIAL CABLE HAVING ONE END CONNECTED TO SAID FIRST TERMINAL; A SECOND TERMINAL FOR RECEIVING A RADIO SIGNAL AT A FREQUENCY WITHIN A PREDETERMINED SECOND RANGE OF FREQUENCIES, SAID SECOND RANGE OF FREQUENCIES BEING LOWER THAN SAID FIRST RANGE OF FREQUENCIES; A SECONE COAXIAL CABLE HAVING ONE END CONNECTED TO SAID SECOND TERMINAL; FIRST AND SECOND FILTERING AND MATCHING NETWORKS ON SAID INSULATING LAYER; FIRST CONNECTING MEANS CONNECTING THE OUTER CONDUCTOR OF SAID COAXIAL CABLE TO SAID FILTERING AND MATCHING NETWORKS; SECOND CONNECTING MEANS CONNECTING THE OUTER CONDUCTOR OF SAID COAXIAL CABLES TO SAID RADIATING LAYER; A THIN CONDUCTIVE STRIP CONNECTED TO SAID FIRST AND SECOND CONNECTING MEANS, SAID THIN STRIP BEING OF A LENGTH EQUAL TO ONE-QUARTER OF A WAVELENGTH OF A PARTICULAR FREQUENCY WITHIN SAID FIRST RANGE OF FREQUENCIES; AND THIRD CONNECTING MEANS CONNECTING THE INNER CONDUCTOR OF SAID COAXIAL CABLES TO SAID FILTERING AND MATCHING NETWORKS SO THAT SAID FIRST FILTER AND MATCHING NETWORK SUBSTANTIALLY RESONATES SAID ANTENNA FOR FREQUENCIES IN SAID FIRST RANGE OF FREQUENCIES AND SAID SECOND FILTERING AND MATCHING NETWORK ACTING IN CONJUNCTION WITH SAID QUARTER WAVELENGTH STRIP SUBSTANTIALLY RESONATES SAID ANTENNA FOR FREQUENCIES WITHIN SAID SECOND RANGE OF FREQUENCIES. 